Constructor and function/method overloading, in computer science, a type of polymorphism where different functions with the same name are invoked based on the data types of the parameters passed
Operator overloading, a form of functional or method overloading where the action being overloaded is an operator, such as + or -

http://www.parashift.com/c++-faq-lite/operator-overloading.html

It allows you to provide an intuitive interface to users of your class, plus makes it possible for templates to work equally well with classes and built-in/intrinsic types.
Operator overloading allows C/C++ operators to have user-defined meanings on user-defined types (classes). Overloaded operators are syntactic sugar for function calls...

Like most dynamically-typed languages, Dart doesn't support overloading. With methods, this isn't much of a limitation because you can always use a different name, but constructors aren't so lucky. To alleviate that, Dart lets you define named constructors:
class Point {
num x, y;
Point(this.x, this.y);
Point.zero() : x = 0, y = 0;
Point.polar(num theta, num radius) {
x = Math.cos(theta) * radius;
y = Math.sin(theta) * radius;
}
}
Here our Point class has three constructors, a normal one and two named ones. You can use them like so:
var a = new Point(1, 2);
var b = new Point.zero();
var c = new Point.polar(Math.PI, 4.0);
Note that we're still using new here when we invoke the named constructor. It isn't just a static method.
. originally published in etdart.blogspot.fi